<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="./styles/index.css" />
</head>

<body>
    <div id="app" class="score-case">
        <div class="table">
            <table>
                <thead>
                    <tr>
                        <th>编号</th>
                        <th>科目</th>
                        <th>成绩</th>
                        <th>操作</th>
                    </tr>
                </thead>

                <tbody v-if="list.length > 0">
                    <tr v-for="(item, index) in list" :key="item.id">
                        <td>{{index + 1}}</td>
                        <td>{{item.subject}}</td>
                        <td>{{item.score}}</td>
                        <td><a href="http://www.baidu.com" @click.prevent="del(item.id)">删除</a></td>
                    </tr>

                </tbody>
                <tbody v-else>
                    <tr>
                        <td colspan="5">
                            <span class="none">暂无数据</span>
                        </td>
                    </tr>
                </tbody>

                <tfoot>
                    <tr>
                        <td colspan="5">
                            <span>总分: {{totalScore}}</span>
                            <span style="margin-left: 50px;">平均分: {{averageScore}}</span>
                        </td>
                    </tr>
                </tfoot>
            </table>
        </div>

        <div class="form">
            <div class="form-item">
                <div class="label">科目: </div>
                <div class="input">
                    <input type="text" placeholder="请输入科目" v-model.trim="subject" />
                </div>
            </div>
            <div class="form-item">
                <div class="label">分数: </div>
                <div class="input">
                    <input type="text" placeholder="请输入分数" v-model.number="score" />
                </div>
            </div>
            <div class="form-item">
                <div class="label"></div>
                <div class="input">
                    <button @click="add" class="submit">添加</button>
                </div>
            </div>
        </div>
    </div>
</body>

<script src="../lib/vue.js"></script>

<script>
    const app = new Vue({
        el: "#app",
        data() {
            return {
                list: [
                    { id: 1, subject: '语文', score: 62 },
                    { id: 7, subject: '数学', score: 89 },
                    { id: 12, subject: '英语', score: 70 },
                ],
                subject: '',
                score: ''
            }
        },
        methods: {
            del(id) {
                this.list = this.list.filter(item => item.id !== id)
            },
            add() {
                if (!this.subject) {
                    alert('请输入科目')
                    return
                }
                if (typeof this.score !== 'number') {
                    alert('请输入正确的成绩')
                    return
                }

                this.list.unshift({
                    id: +new Date(), //变成整数
                    subject: this.subject,
                    score: this.score
                })

                this.subject = ''
                this.score = ''
            }

        },
        computed: {
            totalScore() {
                return this.list.reduce((sum, item) => sum + item.score, 0)
            },
            averageScore() {
                if (this.list.length === 0) {
                    return 0
                }
                return (this.totalScore / this.list.length).toFixed(2)
            }
        }
    })
</script>
</body>

</html>